4.5 Prototyping

Chapter 4.5Additional Resources

As explained within the information and guidelines presented in Chapter 4.5, prototyping is an iterative process through which the innovator builds on his/her learning with each successive model. The steps below have been excerpted from the chapter and are presented with active web links to assist innovators in getting started.

Identify the Questions or Issues to be Addressed through Prototyping

What to Cover – Before translating a design for a solution concept into a working model, clarify the purpose of the prototyping activity to be certain that the goal can be achieved. Define specific questions that must be answered through the creation of the prototype (e.g., will this specific functionality work?) to guide test development. Keep in mind the environment in which the device will be used (e.g., hospital, home use, portable, fixed). This will help define the questions. The answers to these questions should prove a specific element of the design and, in so doing, reduce risk along the development cycle. Resist the temptation to raise questions that are not on the critical path. Remember that these questions can (and should) evolve over time as the invention progresses from idea to product. Each time a prototype is developed, the questions it is designed to answer must be revisited and revised to maximize the benefit of the effort. The answers to these questions should be translated into increasingly specific design requirements.

Where to Look – Go to trade shows in the therapeutic area and look at competitive products. Generate ideas for questions by looking at competitive devices as well as those entirely outside the therapeutic space, and use this as input to help define prototyping goals. Also, study the company’s own designs carefully to isolate the most critical questions to resolve at each stage of prototype development. Interact extensively with the engineering team to define prototyping goals and allow this team to drive the process.

Design the Minimal Model Needed to Answer Those Questions

What to Cover – For the top priority functional block(s), determine the best category of prototype to develop in order to answer the first question that has been defined. Strip out anything and everything from the model that does not explicitly need to be tested. Focus only on the critical path in defining the model. Look at what other companies have done and how they have designed their prototypes. For example, well-known companies have developed highly effective prototypes using nothing more than foam core and paper clips or two syringes and a wood working clamp. A model does not have to be expensive, complex, or made from specialized materials to be effective. Custom prototyping is costly and time-consuming when certain concepts can be proven with ready-made, easily available, and inexpensive materials.

Where to Look – Interact extensively with the engineering team (if one exists) and/or seek input from others who have experience in designing and developing prototypes.

Identify and Prioritize Functional Blocks

What to Cover – Identify the functional blocks associated with the solution being studied. Each block should represent one aspect of the concept and will likely be tied to a distinct engineering discipline based on its characteristics (e.g., mechanical engineering, materials science, and electrical engineering). Prioritize which functional blocks to start with, based on what is known about each one and where the greatest risk/uncertainty exists.

Where to Look – Use the original need criteria, along with more specific functional design requirements that may have emerged through previous analysis (see chapters 4.1 through 4.4) to establish the boundaries for each block and to prioritize them.

Build the Model

What to Cover – Create the prototype focusing only on those elements necessary to address the key question that has been defined (e.g., functionality, interaction of parts, whether the clinical problem can be solved with the design). Prove the concept, retire the most significant risks, and iterate the design along the way. When considering materials, start with basic, inexpensive materials and then gradually progress to more complex, expensive alternatives (e.g., for a mechanical prototype, an inventor might advance from paper and wood to plastics and metals). Similarly, use purchased parts and other off-the-shelf materials whenever possible, reserving the need for specialty or manufactured parts until the later stages of prototype development. As the complexity of models progresses, consider what can realistically be accomplished in-house and what services might require specialized third-party assistance. Given the fact that multiple engineering disciplines may be involved in creating a single prototype, coordination of the efforts across multiple shops may be required.

Where to Look –

Medical Device Register – Database that can be used to identify manufacturers of medical devices and see what companies are working in specific areas of interest.

ASM International Website – A searchable database of modules on materials commonly used for medical device development. Some content may require a license. Has clinically approved devices, including FDA information and literature reviews.

MatWeb – Database of materials. Does not tell which devices use what materials, but it can be used to check the grade of materials.

What to Cover – Use an appropriate bench, simulated use, or tissue test to prove the concept being studied. Define a test requirement (this is often a guess, but grounded in good sense) and develop baseline results. This can determine whether redesign is necessary or redundancy is required. Document the test method and procedures and record results, including technical specification related to fatigue, tensile, force, electrical, and other important issues. Remember that virtually no bench or animal model replicates the human model, so be thoughtful and vigorous in trying to establish a model that is tougher than any probable clinical use. Based on test results, modify the prototype to address clinical, mechanical, and electrical needs. Build a new prototype. Test again. As this process progresses, identify and document increasingly refined technical specifications and design requirements based upon design, user input, and other standards for the device. For more advanced prototypes, use experienced practitioners (doctors, nurses, technicians) to handle the device in the clinical environment and diligently collect their feedback.

FDA Human Factors Considerations – Increasing emphasis on human factors, the study of how people use technology, should be considered throughout the prototyping process, but not at the expense of rapid development if human factors can be built into later designs. These issues are particularly important in developing feelslike/ looks-like/is-like models toward the end of product development.